Packet switched data networks are widely used today. The underlying principle is to chunk data to be transmitted into small packets, each carrying information relating to source and destination, and to switch all these packets independently through the network—a process which is referred to as routing or packet switching.
While packet switching is today done electrically, the definition and development of optical packet switching is currently under way. Optical packets are optical bursts that are to be processed by purely all-optical means, i.e., without optical-to-electrical conversion and electrical processing steps. The optical packets or bursts are delimited by guard time gaps, which enable start and endpoint detection and allow time for the optical processing of the respective packets. An overview over all-optical packet switching can be found in the article “Optical Packet Switching in Core Networks: Between Vision and Reality” by Tarek S. El-Bawab et al, IEEE Communication Magazine Sept. 2002, pages 60-62.
On the other hand, an optical transport network (OTN) has recently been standardized (see ITU-T G.709/Y.1331 02/2001), which will eventually become the predominant transport plane in the future. The principle of the optical transport network is that data signals are transmitted as payload of a framed continuous bit-stream optical signal using one wavelength of a wavelength multiplexed transport signal.
Introduction of optical packet switching systems will probably begin with network islands in for example metropolitan area networks. The connectivity demand, however, will not be restricted to these islands. Though, existing network resources, i.e., the OTN equipment, might be required to interconnect these islands. There will be a need, thus, for sending burst mode optical packet signals as continuous bitrate optical transmission signal over optical transmission lines.